Improvement in screw-drivers



W. L. GILGHRIST. SorevsFDriver.

Patented 'Jan. 8, 1878.

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UNITE STATES PATENT OFFICE.

WILLIAM L. eILoIIRIsr, or FRANKLIN, new HAMPSHIRE.

lM PROVEM IN SCREW-DRIVERS.

Specification forming part of Letters Patent N0. 198,935, dated January 8, 1878; application filed 1 November 20, 1877.

To all whom it may concern:

Be it known that I, WILLIAM L. GILOHRIST, of Franklin, in the county of Merrimack, of the State of New Hampshire, have made a new and useful invention having reference to Screw-Drivers; and do hereby declare the same to be described in the following specification and represented in the accompanying driver, is to readily gage it to, or centralize it with, a sorew-head preparatory to the screw I being revolved by the driver; and my invention consists in the combination of a screwdriver grooved around its shank with atrumpetmouthed gage and a screw arranged with and applied to such driver, substantially as hereinafter explained, and as represented in the drawings, in whic A denotes the screw-driver, provided with a shoulder, a, and also with a wide groove,-b, the latter: being carried transversely around the shank of the driver, and both being arranged in other respects as'represented.

Encompassing the driver is the sliding trumpet-mouthed gage B, which, as shown, is a cylindrical tube, provided with a conical or trumpet mouth, 0, arranged at its lower end. Between the tube and the shoulder is a helical spring, 0, which bears against them, and surrounds the shank of the driver. Furthermore, a stop-screw, d, isscrewed into the tube and the groove 1). This screw and the groovelimit the longitudinal movement of the tube upon the driver, the latter, when at its highest altitude in the tube, having its lower end at the top of the trumpetmouth. I I

On applying the said trumpet-mouth to the head of a screw, and pressing the instrument forward upon such, the said mouth will serve to gage or centralize the screw-driver with respect to the screw-head, whatever its di ameter may be between those of the two ends of the mouth. On the screw-driver beingthus centered, it, on being revolved and being pressed forward, will readily take into or enter the nick of the screw-head, the spring allowing the driver to advance in the gage. Thus,

with the trumpet-gage applied to the screwdriver, aperson, when using the latter, is saved driver, whose tube B can be used as a stationary handle to hold the screw-driver firmly in place on a screw while the screw-driver 'is being revolved in the tube; therefore I claimv The screw-driver A, provided with the wide groove Z), extending entirely around it, in combination with the trumpet-mouthed tubular gage B and the screw (1, arranged with and applied to said driver and groove, substantially as set forth.

W. L. GILOHRIST.

Witnesses:

R. H. EDDY, JOHN R. SNow. 

